The present invention relates to transdermal/dermal, or transmucosal/mucosal drug delivery systems. Transdermal refers to such delivery systems delivering an active that passes through the skin and into the circulating system. Dermal refers to systems with actives delivered to the skin. In transmucosal delivery systems, the active passes through mucosal tissue. In mucosal delivery systems, the active is delivered to the mucosal tissue.
Such delivery systems typically deliver the active via a gel modulated system, membrane modulated system, or an adhesive modulated system. In a gel system the active ingredient, usually a drug, is generally combined with other non-active ingredients to form a gel or paste. This gel is then coated onto a backing member comprising a polymeric film generally on the order of 2 mils or greater in thickness. The gel directly contacts the skin and the overlying backing film includes an adhesive coated surface extending beyond the gel perimeter to hold the assembly on the skin. The membrane modulated system is similar, but has a rate controlling film or membrane over the gelled composition which controls the rate of release of the active composition into the skin.
The adhesive modulated system incorporates the active directly into an adhesive. The adhesive has the ability to control the rate of absorption of the active into the patient's skin. The adhesive mixture is applied to the polymeric backing film which is directly applied to the patient's skin, eliminating the need for the rate controlling membrane and the need for an active containing gel.
Transdermal/dermal, or transmucosal/mucosal delivery systems must reside on the patients skin or mucosa for an extended period of time in order to allow for absorption and subsequent systemic introduction of the active ingredient. However, patients' activities such as bathing and exercising can create forces which act to detach the delivery system from the patients skin or mucosa either directly or by attacking the adhesive. As the residence time of the delivery system increases, the more problematic the long term adhesion of the delivery system becomes.
Currently, there are only three transdermal products that are designed for a seven day residence time. These are Climara® (estradiol), EVRA® (contraceptive steroids), and Catapres® (Clonidine). Climara® and EVRA® both utilize an adhesive modulated system, whereas Catapres® uses the adhesive modulated system in conjunction with an adhesive overlay. The overlay is separately packaged and the patient applies the adhesive overlay only when needed. In this manner the patient can extend the residence time of the delivery system by replacing the used overlays with new ones as they wear out.